1. Field of the Invention
The present invention relates to a sheet conveying apparatus which can correct skew feeding of a sheet and an image forming apparatus including the same.
2. Description of the Related Art
In an image forming apparatus such as a copying machine, a printer, a facsimile, and a multifunction peripheral thereof, the accuracy of an image geometrical characteristic with respect to a sheet is one of important elements affecting image quality, and is degraded when the sheet is fed on the skew. Therefore, in a conventional image forming apparatus, a skew correction unit is provided in a sheet conveying apparatus which conveys the sheet to an image forming portion, and the skew feeding of the sheet is corrected by the skew correction unit in order to prevent the degradation in accuracy of the image geometrical characteristic.
As the skew correction unit described above, there is generally known a shutter system in which a leading edge of a conveying sheet is abutted to align the leading edge of the sheet in a width direction perpendicular to a sheet conveying direction to correct the skew feeding of the sheet. Since the shutter system does not need a driving control system for correcting the skew feeding of the sheet, this system has a great merit on cost.
On the other hand, since the shutter system is configured to move the sheet corrected in skew feeding by rotating a shutter member with a rigidity (stiffness) of the sheet after the leading edge of the sheet is aligned in the width direction, the type of the sheet to be corrected in skew feeding is limited. For example, in the case of a low rigidity sheet (a thin sheet), the sheet is not possible to rotate the shutter and thus may cause a paper jam. In addition, since an apparent rigidity of the sheet is reduced even under a high humidity environment, the same situation may occur.
In this regard, there is disclosed an image forming apparatus which can adjust the contact position of the sheet with respect to the shutter member and make the sheet approach a nip of a conveying roller pair as the rigidity of the sheet is lowered, so that the shutter member is rotatable by a small urging force (see Japanese Patent Laid-Open No. 2006-341993).
However, since the image forming apparatus disclosed in Japanese Patent Laid-Open No. 2006-341993 is configured to change the contact position of the shutter member in cooperation with an opening and closing operation of a manual feeding portion, there is a need to feed the sheet from the manual feeding portion depending on the type of the sheet. The action of setting the sheet on the manual feeding portion is troublesome for a user, and thus the image forming apparatus lacks usability.
Therefore, it is desirable to provide a sheet conveying apparatus and an image forming apparatus having the same which can correct the skew feeding of the sheet with simplicity and ease regardless of the type of the sheet.